Sex differences in onset times of cutaneous thermal sensations across non-noxious to noxious heat intensities.

Sex differences in thermal perception are well documented, but how these differences vary across heat intensities remains unclear. This study investigated sex differences in perception of cutaneous warmth, hot, and pain sensations across contact temperatures ranging from near-threshold to clearly noxious levels. Eight healthy males and eight females were exposed to contact heat stimuli at 42, 46, and 50°C using a Peltier stimulator (6.25 cm2) applied to the left anterior thigh. Onset times for each thermal sensation were recorded, along with heat flux. At rest, skin temperature was significantly higher in males than females (30.2 ± 1.0°C vs. 28.8 ± 0.5°C, P<0.01). Onset times for warmth and hot sensations did not differ between sexes at any temperature. In contrast, females perceived heat pain earlier than males at the contact temperature of 42°C (110 ± 33 s vs. 180 ± 77 s), whereas this sex difference diminished at higher temperatures (46 and 50°C). The temporal distinction between hot and heat pain sensations was evident at 42°C but diminished at higher intensities. Heat flux did not differ between sexes during the initial phase of heating, but heat flux was lower in females during prolonged exposure (P<0.05), suggesting a more rapid rise in skin temperature toward contact temperature. These findings indicate that sex differences in heat pain perception are most pronounced near the nociceptive threshold and diminish with increasing heat intensity. The results highlight the importance of considering both stimulus intensity and temporal dynamics when evaluating sex differences in cutaneous thermal sensitivity.